EFFECT OF SULFATE IONS ON THE STABILITY AND EXCHANGE CHARACTERISTICS OF AN ALUMINUM-INTERLAYERED WYOMING BENTONITE

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Abstract
Al interlayered, Wyoming [USA] bentonite suspensions, containing different amounts of precipitated Al, were equilibrated with SO4 solutions at different concentrations. The amount of Al precipitated as Al-hydroxy complex was 400, 550 and 750 meq/100 g clay, and the concentration of SO4 in solution was 10, 20 and 30 meq/l. On equilibration, the hydroxy-Al interlayer precipitate in the Wyoming bentonite reacted with SO4 ions, and a neutral precipitate of Al hydroxy sulfate was formed. Heating the Wyoming bentonite to 700.degree. C resulted in complete collapse, showing that the precipitate was no longer present in the interlayer space. A crystalline compound of Al hydroxy sulfate was formed as evidenced by X-ray diffraction patterns. In the case of Al-interlayered, Wyoming bentonite suspensions that were not equilibrated with SO4 solution, the Al-hydroxy precipitate remained in the interlayer space and blocked the exchange sites. Treatment of these samples with SO4 solutions resulted in an increase of exchange capacity that was concentration-dependent.